1. Field of the Invention
The present invention relates to a method of laser annealing a semiconductor layer and semiconductor devices produced thereby.
2. Description of the Related Art
The production of semiconductor devices commonly includes one or more steps of laser annealing a semiconductor layer. Typically, but not exclusively, laser annealing is carried out to crystallize a non-single-crystal semiconductor layer, such as an amorphous semiconductor layer of the semiconductor device before it is further processed.
For example, in the production of flat panel display devices such as liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays, an amorphous silicon (a-Si) layer may be laser-annealed to form a polycrystalline silicon (p-Si) layer, by using which thin-film transistors (TFTs) that control the pixels of the LCD or OLED display may be formed.
Depending on the size of the layer to be annealed and the dimensions of the irradiating laser beam, laser annealing may be carried out in two or more sweeps or scans. For example, in the case where laser annealing is carried out on an a-Si semiconductor layer including a 2×2 array of product regions, the laser beam 104 that is used for annealing has an effective working area having a predetermined length x and width y. Typically, the maximum length x of the laser beam is insufficient to irradiate the entire surface of the array. In most cases, therefore, the laser beam is first scanned across a first area of the array, and then the laser beam is scanned across a second area of the array in the same direction. For instance, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 7-249591, in order to ensure that the entirety of the array is annealed, the scanning of the laser beam in the second area is overlapped with the first area, creating an overlap region.
Due to the dual exposure to laser annealing, the overlap region generally exhibits undesirable characteristics, such as unacceptable variations in electrical or physical characteristics. To ensure that these undesirable characteristics do not affect the products manufactured from the array, the overlap region is conventionally arranged outside of the product regions.
As described above, since the conventional overlap region of the semiconductor layer is not usable for the fabrication of the product, due to the problems in electrical or physical characteristics of the overlap region, this part of the array becomes useless. Hence it is difficult to efficiently fabricate products from one array. In addition, if a product of a greater size is to be annealed, an overlap region of laser annealing occurs in the product, leading to the difficulty of fabrication.